The phospholipid-binding protein SESTD1 negatively regulates dendritic spine density by interfering with Rac1-Trio8 signaling pathway.

Cheng-Che Lee,Chiung-Chun Huang,Kuei-Sen Hsu

doi:10.1038/srep13250

Cheng-Che Lee, Chiung-Chun Huang + Show 1 more

Open Access

https://doi.org/10.1038/srep13250

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Journal: Scientific reports	Publication Date: Aug 14, 2015
Citations: 16	License type: CC BY 4.0

Affiliation: National Cheng Kung University

Abstract

Dendritic spines are actin-rich protrusions from neuronal dendrites that harbor the majority of excitatory synapses. The balance of spine formation and retraction may influence dendritic integrity. While knowledge of the molecular mechanisms that promote dendritic spine formation has accumulated, little is known about the factors that limit spine formation. Here, we show that SESTD1, a phospholipid-binding protein containing a lipid-binding SEC14-like domain and two spectrin-repeat cytoskeleton interaction domains, negatively regulates dendritic spine density in cultured hippocampal neurons. Overexpression of SESTD1 decreases dendritic spine density in neurons by interfering with the interaction between Rac1 and its guanine nucleotide exchange factor (GEF) Trio8. Conversely, knockdown of SESTD1 increases dendritic spine density. Further analysis reveals that the SPEC1 domain-mediated interaction with Rac1 is required for SESTD1 activity toward a decrease in dendritic spine density. Transfection of GEF domain of Trio8 into neurons rescues SESTD1-mediated decrease in dendritic spine density. More importantly, overexpression of SESTD1 results in a decrease in the frequency of miniature excitatory postsynaptic currents (mEPSCs), whereas SESTD1 knockdown increases the mEPSC frequency. These results suggest that SESTD1 may act as a negative regulator of the Rac1-Trio8 signaling pathway to reduce dendritic spine density and lower excitatory synaptic transmission in hippocampal neurons.

Highlights

Molecular mechanisms that promote dendritic spine formation and maintenance, but relatively little is known about the factors that limit dendritic spine formation
We further confirmed that SESTD1 expression was high at the early developmental stages of primary hippocampal neurons cultured from E18 rat embryos and its expression levels remained high throughout neuronal maturation (Fig. 1e)
Our findings reveal a concerted mechanism through which SESTD1 binds to Trio[8] via its SPEC1 domain, thereby preventing the recruitment of Rac[1] to the guanine nucleotide exchange factor (GEF) domain of Trio[8], resulting in reduced Rac[1] activity and decreasing dendritic spine density

Summary

Introduction

Molecular mechanisms that promote dendritic spine formation and maintenance, but relatively little is known about the factors that limit dendritic spine formation. SESTD1 (SEC14 and spectrin domains 1) is a recently cloned protein, originally identified as a binding partner of the transient receptor potential channels, TRPC4 and TRPC518. SESTD1 exhibits moderate sequence conservation with the Trio family proteins[20], which may act as an early endosome-specific upstream activator of the Rho family GTPases for neurite elongation[21]. Based on these observations, we hypothesized that SESTD1 may regulate dendritic spine formation and affect synaptic function. We show that SESTD1 is mostly located in the postsynaptic density of neurons, and negatively regulates dendritic spine density by interfering with the Rac1-Trio[8] signaling pathway

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